This invention relates to a structural member of vehicle such as automobile, and more particularly the structural member formed by connecting plate members of light alloy to each other.
It is sometimes found that a chassis of automobile is made of light alloy such as aluminum alloy in order to provide light weight of it and the chassis is provided with various structural members formed by connecting plate members of light alloy.
FIG. 1 is a schematic perspective view for showing one example of a chassis structure of automobile, wherein a side body forming a side surface of the chassis is constituted by a front pillar 1, a center pillar 2 and a rear pillar 3, extending in an upward and downward direction respectively, a roof side rail 4 extending in a forward and rearward direction at upper parts of the pillars and a side sill 5. All these members are structural members having closed sections.
Roof rails 6 connecting the right and left roof side rails, floor frames 7 reinforcing a floor a arranged between the right and left side sills 5 and cross members 8 are also formed by the structural members with closed sections as described above, further each of a pair of right and left front side frames 9 and front upper members 10 extending from a compartment part b toward a forward engine room c are also similarly formed by the structural members with closed sections.
As a means for increasing rigidity of such a structural member having a closed section as described above, prior arts have employed either an increasing of a wall thickness of the member or an enlarging of a section of the member and the like.
However, since Young's modulus of aluminum member is about 1/3 of that of iron and steel member, in the structural member having a closed section formed by plate members of light alloy, even if rigidity is tried to be increased by increasing thickness of the aforesaid plate member, sufficient effect similar to that of the structural member formed by steel plates can not be attained, resulting in that it becomes necessary to enlarge a section of the member and thus various problems may occur.
That is, enlargement of sections of pillars 1, 2 and 3 causes attaining of a superior field of sight to be difficult and a space in the compartment room to be narrowed. Enlargement of sections of the roof side rails 4 and roof rails 6 similarly causes the space in the compartment room to be narrowed or a vehicle height to be increased. Also in the case that the section of each of the side sills 5 is enlarged, the space in the compartment room is narrowed, in addition, riding-on or riding-off characteristic is deteriorated and there occurs a certain difficulty in assuring a ground height of the side sills 5.
A similar effect may occur as for the floor frames 7 and the cross members 8, wherein if their sections are enlarged, a space in the compartment room is narrowed in the case that they are installed in the compartment room and in turn in the case that they are installed outside the compartment room, i.e. below the floor a, a certain difficulty may occur in view of assuring the ground height. In addition, enlargement of a section of each of the front side frames 9 and the front upper members 10 causes a volume of the engine room to be hardly widened.
In view of this fact, Japanese Patent Laid-open No. Sho 60-135375 has a proposal in which the structural members having closed sections are constructed by extruded light metal, although it becomes necessary to arrange connectors between the structural members having closed sections for connecting them, shapes of the structural members having closed sections and the connectors become complex and a high accuracy for them is required.